Packaging material and container

ABSTRACT

A packaging material is provided having a paper layer and a first coating layer laminated thereon, the first coating layer includes a first material and a second material, wherein the first material is a natural rubber or a derivative thereof, and the second material is a material selected from natural resins, waxes and derivatives thereof having permeability into paper. In addition, a packaging material is provided further having a second coating layer laminated having oil resistance, which consists of a biodegradable material.

TECHNICAL FIELD

[0001] The present invention relates to biodegradable packagingmaterials having a moisture barrier property and biodegradablecontainers having a moisture barrier property.

BACKGROUND ART

[0002] Many of food storage containers for preserving instant Chinesenoodles, instant Japanese wheat noodles, instant fried noodles, instantsoups and the like which have been generally used are those in which themain body of the container comprises a foamed resin or any one ofvarious types of synthetic resins.

[0003] However, such a main body of the container comprising a foamedresin or any one of various types of synthetic resins does not generallyhave biodegradability (i.e., a property to be decomposed finally intowater and carbon dioxide by microorganisms after being discarded),therefore, the containers after use have been subjected to incinerationor landfill disposal.

[0004] Further, it has been also suggested that a part of the componentis eluted from the food storage container which comprises the syntheticresin as described above.

[0005] Thus, in recent years, food storage containers as described abovewith a main body composed of paper have been put into practical use.

[0006] However, when the main body is composed of paper alone, moisturebarrier properties or water resistance in such a main body are inferior.Therefore, it was problematic in that external moisture enters into thefood storage container through the main body of the container duringpreserving a food within the food container, thus the food preservedtherein may absorb the moisture resulting in wet food. Alternatively,when the food is eaten after hot water or the like is poured into themain body of the food storage container, the hot water may leak outwardfrom the main body.

[0007] As a consequence, those in which moisture barrier properties orwater resistance are improved in the main body of the container havebeen conventionally used, in general, through providing a coating layerwhich comprises a synthetic resin layer such as polyethylene on the mainbody of the container composed of paper.

[0008] However, when a coating layer which comprises a synthetic resinlayer such as polyethylene is provided on the main body of the containercomposed of paper, such a coating layer does not have biodegradability,leading to similar problems to those in instances where the main body ofthe container comprises a synthetic resin, thereby causing problems ofdisposal of the food container after use.

DISCLOSURE OF THE INVENTION

[0009] The present invention was accomplished in view of the problemsdescribed hereinabove regarding biodegradable paper containers, and anobject of the present invention is to provide a biodegradable packagingmaterial in which a natural moisture proof material is used having amoisture barrier property, which can be also used as a storage containerfor foods, and a biodegradable container.

[0010] The present invention provides a packaging material having apaper layer and a first coating layer laminated thereon, the firstcoating layer comprises a first material and a second material, whereinthe first material is a natural rubber or a derivative thereof, and thesecond material is a material selected from natural resins, waxes andderivatives thereof having permeability into paper.

[0011] According to this invention, a moisture barrier property isimparted by the first coating layer, whilst the both of the firstmaterial and the second material are any naturally occurring product ora derivative thereof having biodegradability. Therefore, a containermanufactured using this packaging material made from paper can bereadily put into disposal after use without harming the environment.

[0012] Such a packaging material according to this invention having thefirst coating layer which comprises the first material and the secondmaterial was made because in instances where a natural rubber or aderivative thereof (first material) is used alone, the coating layer isnot successively adhered to the base composed of paper, which may resultin facilitated peeling of the coating layer from the base composed ofpaper, accompanied by adhesiveness brought to the coating layer. To thecontrary, when a material selected from natural resins, waxes andderivatives thereof having permeability into paper (the second material)is used alone, cracks of the coating layer may be caused upon theformation of the container by heat sealing or the like of this packagingmaterial, leading to inability to sufficiently improve the waterresistance or the moisture barrier property.

[0013] Moreover, the present invention provides a packaging materialhaving a second coating layer laminated having oil resistance, whichconsists of a biodegradable material, in addition to the construction asdescribed above.

[0014] By providing such a second coating layer, water resistance can befurther improved, and a sealant property can be also ameliorated. Inaddition, oil resistance is imparted, which also enables application tofoods including fats and oils.

[0015] When adhesion between the first coating layer and the secondcoating layer is difficult, a paper layer is provided between the firstcoating layer and the second coating layer to effect cohesive laminationof each coating layer to the paper, thereby preventing the secondcoating layer from peeling.

[0016] As the second material of the aforementioned first coating layer,at least one selected from the group consisting of ester gum, dammar,copal, copaiba balsam, benzoin gum, gum olibanum, opopanax, sandarac,Guaiac, mastic, myrrha, Leche de vaca, kauri gum, rosin, fir balsam,elemi, chicle, jelutong, sorva, Venezuela chicle, niger gutta, Chilte,gutta katiau, Tunu, sorbinba, Massaranduba chocolate, Massarandubabalata, balata, Rosidinha, guayule, gutta percha, gutta percha, shellac,urucury wax, carnauba wax, candelilla wax, whale wax, rice bran wax,sugarcane wax, bees wax, wood wax, montan wax, oil stuff seed wax andlanolin may be used. In particular, when ester gum, bees wax, carnaubawax, gutta percha, jelutong or rosin is used, properties as describedabove in a packaging material may be further improved. In addition, whenester gum is used, hot sealing property is improved, thereby allowingsimple formation of the container using the packaging material.

[0017] Furthermore, when the ratio of the first material is too largeupon forming the first coating layer, the coating layer becomes apt tobe peeled from the paper layer, and adhesiveness on the coating layer isalso elevated thereby causing sticky feel. To the contrary, when theratio of the first material in the first coating layer is too small,water resistance and the moisture barrier property are lowered. Hence,the ratio of the first material in the first coating layer is preferably70% by weight or less, and more preferably in the range of from 20 to50% by weight.

[0018] As the biodegradable material of the aforementioned secondcoating layer, at least one selected from the group consisting of poly3-hydroxybutyric acid, polylactic acid, polylactic acid derivatives,polybutylene succinate, modified polymerized resins derived from starch,and a shellac resin can be used. Such materials are not harmful to theenvironment because they have biodegradability.

[0019] Moreover, by using a paper layer having a clay coating on itssurface, permeation into the paper layer of a material in the layercontacted with the paper layer can be prevented.

[0020] The present invention provides a container manufactured using theabove-described packaging material, and such a container is excellent ina moisture barrier property and water resistance, and is not harmful tothe environment because it consists of a biodegradable material. Inparticular, by disposing the second coating layer over the inside faceof the container, application of the container to foods including fatsand oils as their ingredients is enabled, accompanied by improvement ofthe sealant property and water resistance.

[0021] Furthermore, the present invention provides a container whichcomprises an outer container made from paper as a base material and aninner container made from a pulp mold which is fit to the inside of theouter container, wherein the inside face of the outer container has afirst coating layer formed, and the inside face of the inner containerhas a second coating layer formed, with the first coating layercomprising a first material and a second material, wherein the firstmaterial is a natural rubber or a derivative thereof, and the secondmaterial is a material selected from natural resins, waxes andderivatives thereof having permeability into paper, and the secondcoating layer has oil resistance and consists of a biodegradablematerial.

[0022] According to this container, the first coating layer having amoisture barrier property is formed on the outer container, whilst thesecond coating layer having oil resistance is formed on the innercontainer. Therefore, the container has barrier properties such as amoisture barrier property and an oil resistance, as well as a highthermal insulation property on behalf of the inner container made from apulp mold thus provided. In addition, the container is capable of beingdegraded by microorganisms leading to harmlessness to the environmentbecause a biodegradable material is used, with principal material beingpaper or pulp.

[0023] In addition, in the container described above, a thermalinsulation property can be further improved by disposing a spaced layerto a facing zone between the outer container and the inner container.

[0024] Moreover, in the aforementioned container, formation of a uniformsecond coating layer with no seam is enabled through forming the secondcoating layer over the inside face of the inner container as describedabove by a spray coating method with an aqueous solution or an alcoholicsolution of a shellac resin.

[0025] Additionally, a container having a figuration in which an innercontainer made from paper is fit into an outer container made from apulp mold is also allowable. In this instance, highly rigidbiodegradable container can be achieved by fitting a container made frompaper with a structure being in the order from the outside of: firstcoating layer/paper layer/second coating layer, to the outer containermade from a pulp mold.

[0026] Furthermore, the present invention provides a process forproducing a container using a packaging material having at least a paperlayer and a first coating layer laminated, and a biodegradable sealantlayer laminated to the outermost face, in such a manner to allow a partof the packaging material is overlaid, the first coating layer comprisesa first material and a second material, wherein the first material is anatural rubber or a derivative thereof, and the second material is amaterial selected from natural resins, waxes and derivatives thereofhaving permeability into paper, and the process comprises a skivedhemming processing performed such that the outermost face of the endface of the overlaid part where the packaging material is overlaidbecomes the sealant layer.

[0027] When the end face of the packaging material is brought intocontact with for example, an ingredient of the container, permeation ofthe ingredient of the container into the packaging material can beprevented by the skived hemming processing executed. In addition,formation of the container so that the sealant layers are overlaid witheach other is enabled, thereby contributing in favorable formability anda shape retaining property of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a cross sectional view illustrating a layered structureof a packaging material according to the first embodiment.

[0029]FIG. 2 is a cross sectional view illustrating a paper cup which isa container according to the second embodiment.

[0030]FIG. 3 is a cross sectional view illustrating a state of a papercup according to the second embodiment with a food preserved therein.

[0031]FIG. 4 is a cross sectional view illustrating a layered structureof a packaging material according to the third embodiment.

[0032]FIG. 5 is a cross sectional view illustrating a layered structureof a packaging material according to the fourth embodiment.

[0033]FIG. 6 is a cross sectional view illustrating a layered structureof a packaging material according to the fifth embodiment.

[0034]FIG. 7 is a perspective view illustrating a molded tray which is acontainer made from paper according to the sixth embodiment.

[0035]FIG. 8 is a perspective view illustrating a paper cup which is acontainer made from paper according to the seventh embodiment.

[0036]FIG. 9 is a cross sectional view illustrating a layered structureof a packaging material according to the eighth embodiment.

[0037]FIG. 10 is a cross sectional view illustrating a layered structureof a packaging material according to the ninth embodiment.

[0038]FIG. 11 is a perspective view illustrating a paper cup which is acontainer made from paper according to the tenth embodiment.

[0039]FIG. 12 is a cross sectional view illustrating a paper cup whichis a container made from paper according to the eleventh embodiment.

[0040]FIG. 13 is an explanatory drawing illustrating a general moldingprocess of a paper cup according to the eleventh embodiment.

[0041]FIG. 14 is a cross sectional view illustrating a layered structureof a packaging material according to the twelfth embodiment.

[0042]FIG. 15 is a cross sectional view illustrating a layered structureof a packaging material according to the thirteenth embodiment.

[0043]FIG. 16 is a perspective view illustrating a paper cup which is acontainer made from paper according to the fourteenth embodiment.

[0044]FIG. 17 is a cross sectional view illustrating a layered structureof a packaging material according to the fifteenth embodiment.

[0045]FIG. 18 is a cross sectional view illustrating a paper cup whichis a container made from paper according to the sixteenth embodiment.

[0046]FIG. 19 is a cross sectional view accounting for a method ofskived hemming processing upon production of the container made frompaper according to the sixteenth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] The packaging material and the container according to theinvention are specifically explained below with references to theaccompanying drawings.

[0048] (1) First Embodiment

[0049]FIG. 1 is a cross sectional view illustrating a layered structureof a packaging material 1 according to the first embodiment. In FIG. 1,51 denotes a paper layer, and 52 denotes a first coating layer having amoisture barrier property.

[0050] The first coating layer 52 is formed by applying an applicationliquid for coating which contains a natural rubber or a derivativethereof and a material selected from natural resins, waxes andderivatives thereof having permeability into paper, on a paper layer 51followed by drying thereof.

[0051] (2) Second Embodiment

[0052]FIG. 2 is a cross sectional view illustrating a paper cup 10 whichis a container according to the second embodiment. A side body 11 a ofthe paper cup 10 is formed by rolling the packaging material 1 of thefirst embodiment into a cylindrical form which is shrank downward togive a tapered shape so that the first coating layer 52 is positionedover the inside surface, followed by heat sealing of the overlaid part Xof the two layers, as shown in left side in FIG. 2. A bottom lid 11 b ofthe paper cup 10 is formed from the packaging material 1. The bottom lid11 b is mounted to the side body 11 a by placing it into the bottom partof the side body 11 a such that the first coating layer 52 thereofcontacts with the first coating layer 52 of the side body 11 a of thecontainer main body 11, and heat sealing the coating layers 52 with eachother.

[0053] When this paper cup 10 is used as a food storage container, asshown in FIG. 3, a food 2 is put into the container main body 11, andthereafter an opening 12 in the upper part of the container main body 11is allowed to be sealed with a proper lid member 13.

[0054] In the paper cup 10, entry of the outside moisture passingthrough the container main body 11 into the paper cup 10 during storageof the food 2 is suppressed by the first coating layer 52, therebypreventing the food 2 from getting wet through absorbing the moisture,accompanied by preventing a liquid from leaking out of the containermain body 11 when the food 2 is eaten after a liquid such as hot waterwas poured into the container main body 11.

[0055] (3) Third Embodiment

[0056]FIG. 4 is a cross sectional view illustrating a layered structureof the packaging material 3 according to the third embodiment. In FIG.4, 53 denotes a paper layer, 54 denotes a first coating layer having amoisture barrier property, and 55 denotes a second coating layer havingoil resistance and a sealant property. The constitution having the paperlayer 53 and the first coating layer 54 is similar to the packagingmaterial 1 according to the first embodiment.

[0057] The packaging material 3 has a second coating layer 55 providedon the reverse face to the face having the first coating layer 54provided on the paper layer 53. The second coating layer 55 is formedfrom a material of shellac, a modified polymerized resin derived fromstarch, or the like.

[0058] (4) Fourth Embodiment

[0059]FIG. 5 is a cross sectional view illustrating a layered structureof the packaging material 59 according to the fourth embodiment. In thepackaging material 59, the constitution having the paper layer 53 andthe first coating layer 54 is similar to the packaging material 3according to the third embodiment. The packaging material 59 differsfrom the packaging material 3 of the third embodiment in regard to onlyone point that the second coating layer 55 is formed on the firstcoating layer 54.

[0060] The packaging materials 3 and 59 of the third and fourthembodiments may be used for forming the paper cup 10 of the secondembodiment similarly to the packaging material 1 of first embodiment. Tothe paper cup 10 formed using the packaging material 3 or 59 is impartedoil resistance on behalf of the second coating layer 55, and inaddition, water resistance and the sealant property are furtherimproved. In other words, according to the present paper cup 10, entryof the outside moisture passing through the container main body 11 intothe paper cup 10 during storage of the food 2 is suppressed, therebypreventing the food 2 from getting wet through absorbing the moisture,accompanied by preventing a liquid from leaking out of the containermain body 11 when the food 2 is eaten after a liquid such as hot waterwas poured into the container main body 11, as well as avoidingpermeation of fats and oils outside even if the food 2 contains fats andoils.

EXAMPLE

[0061] Experiment 1

[0062] In experiment 1, packaging materials (Experimental Examples A1 toA9) were provided having an altered type of a coating layer provided onthe paper layer, and then a heat sealing property, moisture vaportransmission rate, hot water resistance, a peeling property of thecoating layer and adhesiveness of the coating layer of each of theExperimental Examples were evaluated.

[0063] In Experimental Examples A1 to A9, 240 g/m² board was used as thematerial of the paper layer. In addition, as materials for use in theapplication liquid for the coating layer provided on one face of thepaper layer, a natural rubber, and ester gum having the softening pointTm of 120° C. as the material selected from natural resins, waxes andderivatives thereof having permeability into paper were used. Thesematerials were used after adjusting their total weight ratio to accountfor 20% by weight of 100% by weight of the application liquid bydissolving in cyclohexane. Ratio of the natural rubber and ester gum wasas shown in Table 1 in connection with each of Experimental Examples A1to A9.

[0064] Each application liquid for coating which was prepared in such amanner was each applied on one face of the aforementioned paper layerusing a bar coater #40 (manufactured by R.D. Special Co.), and was airdried. Thereafter, each application liquid for coating was applied againusing the bar coater #40 followed by air drying. A coating layer wasformed on each one face of the paper layer to give the packagingmaterials of Experimental Examples A1 to A9.

[0065] Next, evaluation of thus obtained packaging materials ofExperimental Examples A1 to A9 was conducted for each heat sealingproperty, moisture vapor transmission rate, hot water resistance,peeling property of the coating layer and adhesiveness of the coatinglayer. The results are shown in Table 1.

[0066] The heat sealing property herein was evaluated by overlaying eachcoating layer provided on the packaging material, heat sealing using animpulse sealer (HUJI IMUPULSE Co., Ltd. HUJI IMPULSE Sealer) with thetemperature at the bonded part of 180° C. and examining the adhesionstate. Favorable adhesion state was evaluated as ◯; and insufficientadhesion was evaluated as X.

[0067] In respect of the moisture vapor transmission rate, 50 g ofcalcium chloride was charged into each bag which was prepared with eachpackaging material respectively, and each bag was sealed. Afterpreserving each bag in a constant temperature and humidity atmosphere,at the temperature of 40° C. and humidity of 90% for 24 hours, increaseof the weight was determined, and the increased weight per unit area perday was identified as moisture vapor transmission rate (g/m²·day).

[0068] In connection with the water resistance, to each containermanufactured using each packaging material was poured hot water of 100°C., left to stand for 20 minutes, and the leaking of the hot water fromthe container was examined. No occurrence of leaking was evaluated as ◯;occurrence of slight swelling of the container was evaluated as Δ; andoccurrence of leaking was evaluated as X.

[0069] In regard to the peeling property of the coating layer, thecoating layer provided on each packaging material was rubbed with afinger. Accordingly, no occurrence of peeling of the coating layer wasevaluated as ◯; occurrence of slight peeling of the coating layer wasevaluated as Δ; and occurrence of peeling of the coating layer wasevaluated as X.

[0070] With regard to the adhesiveness of the coating layer, the coatinglayer provided on each packaging material was touched with hands. Nosticky feeling was evaluated as ◯; slight but not raising anxious stickyfeeling was evaluated as Δ; and the presence of sticky feeling wasevaluated as X. TABLE 1 Experimental Example A1 A2 A3 A4 A5 A6 A7 A8 A9Natural rubber (% by weight) 100 90 70 50 30 25 20 15 5 Ester gum havingTm of 120° C. 0 10 30 50 70 75 80 85 95 (% by weight) Heat sealingproperty ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X Moisture vapor transmission rate 663 183 14279 65 65 35 71 298 (g/m² · day) Water resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ XPeeling property of coating layer X X ◯ ◯ ◯ ◯ ◯ ◯ ◯ Adhesiveness ofcoating layer X X Δ ◯ ◯ ◯ ◯ ◯ ◯

[0071] As is clear from these results, in instances where the coatinglayer was provided using a natural rubber, and ester gum having thesoftening point Tm of 120° C. as the material selected from naturalresins, waxes and derivatives thereof having permeability into paper,when the amount of the natural rubber in the coating layer is too large,the coating layer becomes liable to peel, and in addition, theadhesiveness in the coating layer is increased. To the contrary, whenthe amount of the natural rubber in the coating layer is too small, heatsealing property, water resistance and moisture barrier property werelowered. Further, when the amount of the natural rubber in the coatinglayer fell within the range of from 20 to 50% by weight, coating layerscould be achieved which are excellent in any terms of heat sealingproperty, moisture vapor transmission rate, water resistance, peelingproperty of the coating layer and the adhesiveness of the coating layer.

[0072] Experiment 2

[0073] In Experiment 2, packaging materials (Experimental Examples A10to A12) were prepared having altered type of the coating layer providedon the paper layer, and similarly to Experiment 1, evaluation of thepackaging material of each Experimental Example was conducted for theheat sealing property, moisture vapor transmission rate, hot waterresistance, peeling property of the coating layer and adhesiveness ofthe coating layer.

[0074] In Experimental Examples A10 to A12, 240 g/m² board was used asthe paper layer, similarly to Experiment 1. As the material of theapplication liquid for the coating layer provided on one face of thepaper layer, a natural rubber and ester gum were used. Ester gum used ineach Experimental Example is as follows: in Experimental Example A10,ester gum having the softening point Tm of 109° C.; in ExperimentalExample A11, ester gum having the softening point Tm of 120° C. andester gum having the softening point Tm of 109° C.; and in ExperimentalExample A12, ester gum having the softening point Tm of 93° C. In eachExperimental Example, the application liquid for coating was preparedwith the ratio of ester gum and the natural rubber set as shown in Table2 below, and their total weight ratio adjusted to account for 20% byweight of 100% by weight of the application liquid by dissolving incyclohexane.

[0075] Then, each packaging material of any one of Experimental ExamplesA10 to A12 was obtained by using each application liquid for coatingprepared in such a manner and forming each coating layer on one face ofthe paper layer similarly to Experiment 1.

[0076] Next, evaluation of thus resulting each packaging material of anyone of Experimental Examples A10 to A12 obtained in the aforementionedmanner was also conducted in a similar manner to Experiment 1 for theheat sealing property, moisture vapor transmission rate, heatresistance, peeling property of the coating layer and adhesiveness ofthe coating layer. The results are shown in Table 2. TABLE 2Experimental Example A6 A10 A11 A7 A12 Natural rubber (% by weight) 2525 35 20 20 Ester gum having Tm of 120° C. 75 — 15 80 — (% by weight)Ester gum having Tm of 109° C. — 75 50 — — (% by weight) Ester gumhaving Tm of 93° C. — — — — 80 (% by weight) Heat sealing property ◯ ◯ ◯◯ ◯ Moisture vapor transmission 65 167 324 35 458 rate (g/m² · day)Water resistance ◯ ◯ ◯ ◯ ◯ Peeling property of coating ◯ ◯ ◯ ◯ ◯ layerAdhesiveness of coating layer ◯ ◯ ◯ ◯ X

[0077] As a consequence, in instances where the amount of the naturalrubber was identical, when packaging materials with the coating layerprovided using ester gum having different softening point Tm werecompared, less moisture vapor transmission rate was exhibited by thepackaging material with the coating layer provided using ester gumhaving the softening point Tm of 120° C. compared to the packagingmaterial with the coating layer provided using ester gum having thesoftening point Tm of 109° C. or the packaging material with the coatinglayer provided using ester gum having the softening point Tm of 93° C.

[0078] Experiment 3

[0079] In Experiment 3, packaging materials (Experimental Examples B1 toB7) were prepared having altered type of the coating layer provided onthe paper layer, and similarly to Experiment 1, evaluation of eachExperimental Example was conducted for the heat sealing property,moisture vapor transmission rate, hot water resistance, peeling propertyof the coating layer and adhesiveness of the coating layer.

[0080] In Experimental Examples B1 to B7, 240 g/m² board was used as thepaper layer, similarly to Experiment 1. Upon providing the coating layeron one face of the paper layer in Experimental Examples B1 to B7, anatural rubber, and rosin having the softening point Tm of 77° C. as thematerial selected from natural resins, waxes and derivatives thereofhaving permeability into paper. Each application liquid for coating wasprepared with the ratio of the natural rubber and this rosin set asshown in Table 3 below, and the total weight ratio of the natural rubberand the rosin adjusted to account for 20% by weight by dissolving incyclohexane, respectively.

[0081] Then, each packaging material of any one of Experimental ExamplesB1 to B7 was obtained by using each application liquid for coatingprepared in such a manner and forming each coating layer on one face ofthe paper layer similarly to Experiment 1.

[0082] Next, evaluation of thus resulting each packaging material of anyone of Experimental Examples B1 to B7 obtained in the aforementionedmanner was also conducted in a similar manner to Experiment 1 for theheat sealing property, moisture vapor transmission rate, hot waterresistance, peeling property of the coating layer and adhesiveness ofthe coating layer. The results are shown in Table 3. TABLE 3Experimental Example B1 B2 B3 B4 B5 B6 B7 Natural rubber (% by weight)90 70 60 50 30 20 5 Rosin (% by weight) 10 30 40 50 70 80 95 Heatsealing property X X X X X X X Moisture vapor transmission 206 213 200148 129 214 324 rate (g/m² · day) Water resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ Peelingproperty of coating layer X X Δ ◯ ◯ ◯ ◯ Adhesiveness of coating layer XX X X Δ ◯ ◯

[0083] As a consequence, the packaging material having the coating layerformed using rosin having the softening point Tm of 77° C. as thematerial selected from natural resins, waxes and derivatives thereofhaving permeability into paper exhibited favorable water resistance andpeeling property similarly to the packaging material having the coatinglayer formed using ester gum, but the heat sealing property and theadhesiveness of the coating layer were inferior. However, such drawbackscan be overcome by thickening the coating layer, allowing other naturalresin or wax mixed therein, or providing a second coating layer havingadhesiveness on the coating layer.

[0084] Experiment 4

[0085] In Experiment 4, packaging materials (Experimental Examples C1 toC7) were prepared having altered type of the coating layer provided onthe paper layer, and similarly to Experiment 1, evaluation of thepackaging material of each Experimental Example was conducted for theheat sealing property, moisture vapor transmission rate, waterresistance, peeling property of the coating layer and adhesiveness ofthe coating layer.

[0086] In Experimental Examples C1 to C7, 240 g/m² board was used as thepaper layer, similarly to Experiment 1. Upon providing the coating layeron one face of the paper layer, in Experimental Example C1, a naturalrubber, and carnauba wax having the melting point of 78 to 84° C. as thematerial selected from natural resins, waxes and derivatives thereofhaving permeability into paper were used, and in Experimental ExamplesC2 to C7, a natural rubber, and any combination of carnauba wax havingthe melting point of 78 to 84° C. and ester gum having the softeningpoint Tm of 109° C. or ester gum having the softening point Tm of 120°C. were used.

[0087] Each application liquid for coating was then prepared with theratio of the natural rubber and carnauba wax, ester gum having thesoftening point Tm of 109° C. and ester gum having the softening pointTm of 120° C. set as shown in Table 4 below, and the total weight ratioof the natural rubber and the material selected from natural resins,waxes and derivatives thereof having permeability into paper adjusted toaccount for 20% by weight by dissolving in cyclohexane, respectively.

[0088] Then, each packaging material of any one of Experimental ExamplesC1 to C7 was obtained by using each application liquid for coatingprepared in such a manner and forming each coating layer on one face ofthe paper layer similarly to Experiment 1.

[0089] Next, evaluation of thus resulting each packaging material of anyone of Experimental Examples C1 to C7 obtained in the aforementionedmanner was also conducted in a similar manner to Experiment 1 for theheat sealing property, moisture vapor transmission rate, waterresistance, peeling property of the coating layer and adhesiveness ofthe coating layer. The results are shown in Table 4. TABLE 4Experimental Example C1 C2 C3 C4 C5 C6 C7 Natural rubber (% by weight)20 15 15 20 15 20 15 Carnauba wax (% by weight) 80 10 20 10 10 10 10Ester gum having Tm of 120° C. — — — — 75 70 65 (% by weight) Ester gumhaving Tm of 109° C. — 75 65 70 — — — (% by weight) Heat sealingproperty X ◯ ◯ ◯ ◯ ◯ ◯ Moisture vapor transmission rate 70 51 66 53 4950 63 (g/m² · day) Water resistance X Δ X ◯ ◯ ◯ ◯ Peeling property ofcoating layer ◯ ◯ ◯ ◯ ◯ ◯ ◯ Adhesiveness of coating layer ◯ ◯ ◯ ◯ ◯ ◯ ◯

[0090] As a consequence, the packaging material having the coating layerformed using carnauba wax alone having the melting point of 78 to 84° C.as the material selected from natural resins, waxes and derivativesthereof having permeability into paper exhibited less heat sealingproperty and water resistance in comparison with the packaging materialhaving the coating layer formed using ester gum, but the heat sealingproperty and water resistance were improved when carnauba wax and estergum were used in combination.

[0091] Experiment 5

[0092] In Experiment 5, packaging materials (Experimental Examples D1 toD3) were prepared having altered type of the coating layer provided onthe paper layer, and similarly to Experiment 1, evaluation of eachExperimental Example was conducted for the heat sealing property,moisture vapor transmission rate, water resistance, peeling property ofthe coating layer and adhesiveness of the coating layer.

[0093] In Experimental Examples D1 to D3, 240 g/m² board was used as thepaper layer, similarly to Experiment 1. Upon providing the coating layeron one face of the paper layer, in Experimental Examples D1 and D2, anatural rubber, and candelilla wax having the melting point of 66 to 70°C. as the material selected from natural resins, waxes and derivativesthereof having permeability into paper; and in Experimental Example D3,a natural rubber, the aforementioned candelilla wax and ester gum havingthe softening point Tm of 120° C. were used in a ratio as shown in Table5 below. These were dissolved in cyclohexane respectively, and thus eachapplication liquid for coating was prepared so that the total weightratio of the natural rubber and the material selected from naturalresins, waxes and derivatives thereof having permeability into paperaccounted for 20% by weight.

[0094] Then, each packaging material of any one of Experimental ExamplesD1 to D3 was obtained by using each application liquid for coatingprepared in such a manner and forming each coating layer on one face ofthe paper layer, similarly to Experiment 1.

[0095] Next, evaluation of thus resulting each packaging material of anyone of Experimental Examples D1 to D3 obtained in the aforementionedmanner was also conducted in a similar manner to Experiment 1 for theheat sealing property, moisture vapor transmission rate, waterresistance, peeling property of the coating layer and adhesiveness ofthe coating layer. The results are shown in Table 5. TABLE 5Experimental Example D1 D2 D3 Natural rubber (% by weight) 20 25 35Candelilla wax (% by weight) 80 75 50 Ester gum having Tm of 120° C. — —15 (% by weight) Heat sealing property X X X Moisture vapor transmissionrate (g/m² · day) 31 38 40 Water resistance X X ◯ Peeling property ofcoating layer ◯ ◯ ◯ Adhesiveness of coating layer X X X

[0096] As a consequence, the packaging material having the coating layerformed using candelilla wax having the melting point of 66 to 70° C. asthe material selected from natural resins, waxes and derivatives thereofhaving permeability into paper exhibited less heat sealing property,water resistance and adhesiveness of the coating layer in comparisonwith the packaging material having the coating layer formed using estergum, but water resistance was improved when candelilla wax and ester gumwere used in combination. It is believed that use of ester gum atadditional higher ratio may improve also the heat sealing property andadhesiveness of the coating layer similarly to the above instance inwhich carnauba wax and ester gum were used in combination.

[0097] Experiment 6

[0098] In Experiment 6, packaging materials (Experimental Examples E1 toE3) were prepared having altered type of the coating layer provided onthe paper layer, and similarly to Experiment 1, evaluation of eachExperimental Example was conducted for the heat sealing property, waterresistance, moisture vapor transmission rate and oil resistance.

[0099] In Experimental Examples E1 to E3, 240 g/m² board was used as thepaper layer, similarly to Experiment 1. Upon providing the coating layeron one face of the paper layer, a natural rubber and ester gum havingthe softening point Tm of 120° C. as the material selected from naturalresins, waxes and derivatives thereof having permeability into paperwere used in a weight ratio of the natural rubber and ester gum of75:25. These were dissolved in cyclohexane respectively, and thus eachapplication liquid for coating was prepared so that the total weightratio of the natural rubber and the material selected from naturalresins, waxes and derivatives thereof having permeability into paperaccounted for 40% by weight.

[0100] Then, each application liquid for coating was applied on one faceof the aforementioned paper layer using a bar coater #40 (manufacturedby R.D. Special Co.), and was air dried. In Experimental Example E1, apackaging material having the coating layer provided on one face of thepaper layer as described above was used. To the contrary, inExperimental Example E2, the packaging material used was produced bypreparing a second application liquid for coating including shellacdissolved in ethanol to give 25% by weight, applying this secondapplication liquid for coating on the above-described coating layerusing a bar coater #40 (manufactured by R.D. Special Co.) and air dryingto provide a second coating layer on the above-described coating layer.

[0101] Further, in Experimental Example E3, the packaging material usedwas produced by preparing a second application liquid for coatingincluding shellac dissolved in ethanol to give 25% by weight, applyingthis second application liquid for coating on the reverse face to theabove-described coating layer using a bar coater #40 (manufactured byR.D. Special Co.) and air drying to provide a second coating layer onthe reverse face to the above-described coating layer of the paperlayer.

[0102] Next, evaluation of each packaging material of any one ofExperimental Examples E1 to E3 obtained in the aforementioned manner wasconducted for heat sealing property, water resistance and moisture vaportransmission rate. In addition, evaluation for oil resistance was alsoconducted. The results are shown in Table 6.

[0103] Evaluation of the heat sealing property, water resistance andmoisture vapor transmission rate was conducted in a similar manner as inExperiment 1. In connection with the evaluation of oil resistance, bluecolored terpene oil was dropped to the face having the coating layerprovided which contains the natural rubber of each packaging material,and left to stand for 1 hour. Permeation of the colored terpene oil wasthen examined on the reverse face to the dropped face of each packagingmaterial. Absence of permeation was evaluated as ◯; and the presence ofpermeation was evaluated as X. TABLE 6 Experimental Example E1 E2 E3heat sealing property ◯ ◯ ◯ water resistance ◯ ◯ ◯ moisture vaportransmission rate 48.8 47.7 37.8 (g/m² · day) oil resistance X ◯ ◯

[0104] As a consequence, the packaging materials of Experiment ExamplesE2 and E3 having the second coating layer provided in which shellac wasused in addition to the coating layer including the natural rubber, ascoating layers of the paper layer, exhibited improved oil resistance incomparison with the packaging material of Experiment Example E1 havingno second coating layer provided.

[0105] Moreover, the packaging material of Experiment Example E3 havingthe second coating layer provided to the paper layer in which shellacwas used, on the reverse face to the coating layer including the naturalrubber, exhibited less moisture vapor transmission rate in comparisonwith the packaging materials of Experiment Examples E2 and E3, and themoisture barrier property was improved accordingly.

[0106] (5) Fifth Embodiment

[0107]FIG. 6 is a cross sectional view illustrating a layered structureof a packaging material 4 according to the fifth embodiment. In FIG. 6,5 and 7 denote a paper layer, 6 denotes a first coating layer having amoisture barrier property, and 8 denotes a second coating layer havingoil resistance.

[0108] As materials for the paper layers 5 and 7, carton board, ivorypaper, cup body paper or the like which is excellent in flexibility ispreferably used taking into account of the container formability, andthose having weighing capacity of approximately 80 to 160 g/m² may besuitably used.

[0109] The first coating layer 6 has a moisture barrier property, whichincludes a natural rubber or a derivative thereof and a natural resin, awax and a derivative thereof? having permeability into paper, preferablyincludes a natural rubber and ester gum. For example, a mixture of fournatural products, i.e., a natural rubber, ester gum, modified rosin andnatural wax can be used as the material. In this case, illustrativemixing ratio may be: natural rubber/ester gum/modified rosin/naturalwax=20/8/57/9 (ratio by solid content), or the like. Furthermore,jelutong, gutta percha, chicle, sorva, or the like can be used neat oras a mixture, instead of ester gum rosin or the like.

[0110] In order to impart a moisture barrier property which are nearlyequal to those of polyethylene to the first coating layer 6, thicknessof the first coating layer 6 of approximately 30 to 40 μm is required.Examples of general method of application of the first coating layer 6on the paper layer 5 include sandwich lamination by an extrusionlamination method, or a method in which heat lamination is performedafter coating (thermal lamination). The first coating layer 6 may beformed through sandwich lamination of the paper layer 5 and the paperlayer 7 by the aforementioned method.

[0111] The second coating layer 8 has a sealant property and waterresistance in addition to oil resistance, which is formed on the reverseface to the face provided with the first coating layer 6 of the paperlayer 7. The second coating layer 8 has biodegradability, and is a layercontaining any one of poly 3-hydroxy butyric acid (PHB), polylactic acid(PLA), a polylactic acid derivative, polybutylene succinate, a modifiedpolymerized resin derived from starch, as well as a shellac resin or thelike as a predominant material. Preferably, the second coating layer 8is a layer comprising any of these resins itself, or comprising amixture of these resins.

[0112] Application method of the second coating layer 8 on the paperlayer 7 is generally an extrusion lamination method. However, ininstances of a modified polymerized resin derived from starch, filmmaking is required through dissolution in a solvent or a heat treatmentof a liquid obtained by emulsification.

[0113] Lamination of each of these layers is carried out by any one ofthe following methods, in general. Specifically, either one of thefollowing methods may be employed: a method in which after applying thesecond coating layer 8 on the paper layer 7 (according to extrusionlamination method or liquid coating method), sandwich lamination of thepaper layer 7 side of this complex material and the paper layer 5 isperformed via the first coating layer 6 which was formed by extrusion;and a method in which after sandwich lamination of the paper layer 5 andthe paper layer 7 via the first coating layer 6 which was formed byextrusion, the second coating layer 8 is applied on the reverse face tothe face that contacts with the first coating layer of the paper layer 7(according to extrusion lamination method or liquid coating method).

[0114] (6) Sixth Embodiment

[0115]FIG. 7 is a perspective view illustrating a molded tray 14 whichis a container made from paper according to the sixth embodiment. Themolded tray 14 is produced by a molding process such as a pressureforming process or a vacuum forming process after cutting the packagingmaterial 4 of the fifth embodiment into a desired size.

[0116] (7) Seventh Embodiment

[0117]FIG. 8 is a perspective view illustrating a paper cup 15 which isa container made from paper according to the seventh embodiment. Thepaper cup 15 is produced by appropriate processing of the packagingmaterial 4 of the fifth embodiment to give a side body member and abottom part member followed by use of a generally known forming machineof paper cups.

EXAMPLES

[0118] The fifth to seventh embodiments are explained below in moredetail by way of Examples.

Example 1

[0119] No coated cup body paper having the weighing capacity of 140 g/m²was prepared as a paper layer 7, and to this cup body paper wascoextruded LACEA (Mitsui Chemicals, Inc.) which is PLA that becomes amaterial of the second coating layer 8 with polyethylene by a meltextrusion machine. After applying to give the thickness of 30 μmfollowed by rolling up, thus coextruded polyethylene was peeled from PLAand rolled up again. Accordingly, composite paper comprising: cup bodypaper (paper layer) 7/second coating layer 8 was produced.

[0120] Next, a no coated cup body paper having the weighing capacity of140 g/m² was prepared as a paper layer 5, and sandwich laminationbetween the composite paper described above was performed throughmelting extrusion of a mixed material of: natural rubber./estergum/modified rosin/natural wax=20/8/57/9 (ratio of solid content).Thickness of the mixed material which becomes the first coating layer 6was 40 μm. Moreover, the melt extrusion temperature was 200° C. Themodified rosin which was used was modified rosin ester (trade name:PENSEL (R) D-160, manufactured by Arakawa Chemical Industries, Ltd.)(the same in Example below).

[0121] Accordingly, the packaging material 4 of Example 1 was obtainedwhich comprised: cup body paper 5 having the weighing capacity of 140g/m²/first coating layer 6 having the thickness of 40 μm/cup body paper7 having the weighing capacity of 140 g/m²/second coating layer 8 havingthe thickness of 30 μm which is PLA.

Example 2

[0122] First, composite paper which is similar to that in Example 1 wasproduced which comprised: cup body paper (paper layer) 7/second coatinglayer 8. Then, on one face of no coated cup body paper 5 having theweighing capacity of 140 g/m² was applied twice a 5:1 mixed solution ofa 50% solution of jelutong in chloroform and a 50% solution of dammar inchloroform with a bar coater #26, followed by drying to form the firstcoating layer 6. Next, the composite paper described above and the cupbody paper 5 were subjected to sandwich lamination so that the cup bodypaper 7 is brought into contact with the first coating layer 6. Thethickness of the first coating layer was 40 μm.

[0123] Accordingly, the packaging material 4 of Example 2 was obtainedwhich comprised: cup body paper 5 having the weighing capacity of 140g/m²/first coating layer 6 having the thickness of 40 μm/cup body paper7 having the weighing capacity of 140 g/m²/second coating layer 8 havingthe thickness of 30 μm.

Comparative Example 1

[0124] On one face of cup body paper having the weighing capacity of 250g/m² was applied PLA in a similar manner to that in Example 1 to givethe thickness of 30 μm thereby obtaining the packaging material ofComparative Example 1 which comprised: cup body paper having theweighing capacity of 250 g/m²/PLA having the thickness of 30 μm.

Comparative Example 2

[0125] On one face of cup body paper having the weighing capacity of 250g/m² was applied polyethylene in a similar manner to that in Example 2to give the thickness of 30 μm thereby obtaining the packaging materialof Comparative Example 2 which comprised: cup body paper having theweighing capacity of 250 g/m²/polyethylene having the thickness of 30μm.

Comparative Example 3

[0126] A mixed material of a natural rubber, ester gum, modified rosin,a natural wax with the same ratio of the solid content as in Example 1was slot nozzle coated at 250° C. on one face of cup body paper havingthe weighing capacity of 250 g/m² to form a moisture proof layer havingthe thickness of 40 μm. Thus, the packaging material of ComparativeExample 3 was obtained which comprised: cup body paper having theweighing capacity of 250 g/m²/moisture proof layer having the thicknessof 40 μm.

[0127] Experiment 7

[0128] Any one of the 5 types of packaging materials according to theaforementioned Examples 1 and 2, and Comparative Examples 1 to 3 wasappropriately processed to yield a side body member and a bottom partmember. Using a generally known forming machine of paper cups, papercups were produced having the height of 107 mm, bore diameter of 94.5mm, bottom diameter of 64.3 mm and taper angle of 6.5° so that the paperlayer is circumferentially positioned.

[0129] The moisture barrier property, oil resistance, sealing propertyand biodegradability of these 5 types of the paper cup were measured andevaluated according to the following process. The results are shown inTable 7.

[0130] The moisture barrier property was evaluated by charging 50 g ofcalcium chloride into a sample cup, tight sealing the cup with anappropriate lid member followed by leaving to stand in an atmosphere atthe temperature of 40° C. and humidity of 90%. Changes in weight due tothe transmitted moisture were measured, and the change in weight of lessthan 80 g/m²·day was evaluated as ◯; and the change in weight of 80g/m²·day or greater was evaluated as X.

[0131] In regard to the oil resistance, curry powder dissolved in hotwater was charged into a sample cup, and left at the temperature of 60°C. for 24 hours, and the permeation degree into the paper was visuallyobserved. Absence of the permeation was evaluated as ◯; and presence ofthe permeation was evaluated as X.

[0132] In connection with the sealing property, the formed sample cupwas destroyed, and adhesiveness of the side body joint part and thebottom joint part was visually observed. Presence of peeling with paperscaling at the adhered part was evaluated as ◯; and absence of paperscaling leading to judgment as insufficient adhesion was evaluated as X.

[0133] Biodegradability was evaluated according to JIS K6950“Plastic—Method of Testing Degree of Aerobic Biodegradation by ActivatedSludge”. Presence of degradation was evaluated as ◯; and absence ofdegradation was evaluated as X. TABLE 7 Moisture Barrier Oil SealingProperty Resistance property Biodegradability Example-1 ◯ ◯ ◯ ◯ Example2 ◯ ◯ ◯ ◯ Comparative X ◯ ◯ ◯ Example 1 Comparative ◯ ◯ ◯ X Example 2Comparative ◯ X ◯ ◯ Example 3

[0134] Accordingly, paper cups produced using the packaging materials ofExample 1 and Example 2 in which the paper layer, the first coatinglayer, the paper layer and the second coating layer are laminated inthis order are biodegradable paper cups that are excellent in moisturebarrier property and oil resistance. In addition, by laminating in theorder of: paper layer/first coating layer/paper layer/second coatinglayer in such a manner, better adhesiveness is achieved between thefirst and the second coating layers in comparison with the case oflamination in the order of: paper layer/first coating layer/secondcoating layer. For example, when the paper cup was formed in the seventhembodiment, in instances of constitution of: paper layer/first coatinglayer/second coating layer, there may be a case in which peeling occursbetween the first coating layer and the second coating layer, however,in instances of constitution of: paper layer/first coating layer/paperlayer/second coating layer, such problems are not caused.

[0135] (8) Eighth Embodiment

[0136]FIG. 9 is a cross sectional view illustrating a layered structureof a packaging material 16 according to the eighth embodiment. In FIG.9, 17 denotes a paper layer, 18 denotes a first coating layer having amoisture barrier property, and 19 denotes a second coating layer.

[0137] For the paper layer 17, cup body paper having comparativelyexcellent flexibility is preferably used, and one having the weighingcapacity of approximately 200 to 280 g/m² can be suitably used.

[0138] The first coating layer 18 is applied on the paper layer 17. Thefirst coating layer 18 comprises a natural rubber or a derivativethereof, and a natural resin, a wax and a derivative thereof havingpermeability into paper. For example, a mixture of three naturalproducts, i.e., a natural rubber, modified rosin and wax can be used asthe material. In this case, illustrative mixing ratio may be: naturalrubber/modified rosin/wax=20/64/16 (ratio by solid content). Desiredmoisture barrier property can be achieved by the first coating layer 18with the application amount of approximately 25 g/m².

[0139] Application of the first coating layer 18 on the paper layer 17may be generally carried out by extrusion coating or nozzle coating witheach natural product constituting the first coating layer 8 in adissolved state. Alternatively, the first coating layer 8 may be alsoformed through dissolving each of the natural products described abovein butyl acetate as a solvent to give 30 to 50% by weight of the solidcontent, followed by comma coating of the solution.

[0140] The second coating layer 19 comprises an ester compound of lauricacid and dextrin, and is formed on the first coating layer 18 asdescribed above. The second coating layer 19 has oil resistance and asealant property. Examples of the ester compound of lauric acid anddextrin which can be preferably used include Cornpol CPR-D703 (NihonCornstarch corporation). The second coating layer 19 may be formed byapplying a 20 to 30% by weight (solid content) solution of theaforementioned Cornpol in ethyl acetate as a solvent by a comma coater(lip coater) in an amount of approximately 20 to 40 g/m² (solidcontent).

[0141] (9) Ninth Embodiment

[0142]FIG. 10 is a cross sectional view illustrating a layered structureof a packaging material 20 according to the ninth embodiment. Thepackaging material 20 of this embodiment has a layered structure havinga second paper layer 21 provided between the first coating layer 18 andthe second coating layer 19 of the packaging material 16 according tothe eighth embodiment.

[0143] In this embodiment, for both of the paper layer 17 and the secondpaper layer 21, cup body paper having the weighing capacity ofapproximately 130 to 150 g/m² may be used. The application amount of thefirst coating layer 18 and the second coating layer 19 is essentiallyequal to those in the packaging material 16 according to the eighthembodiment.

[0144] (10) Tenth Embodiment

[0145]FIG. 11 is a perspective view illustrating a paper cup 22 which isa container made from paper according to the tenth embodiment. The papercup 22 is produced by appropriately processing the packaging material 16or 20 according to the eighth or ninth embodiment to yield a side bodymember and a bottom part member followed by use of a generally knownforming machine of paper cups.

EXAMPLES

[0146] The eighth to tenth embodiments are explained below in moredetail by way of Examples.

Example 3

[0147] Cup body paper having the weighing capacity of 250 g/m² wasprepared as a paper layer 17, and on the reverse face of this cup bodypaper was applied a mixed material of natural rubber with a mixing ratioof: natural rubber/modified rosin/wax=20/64/16, which had been melted at200° C., by a nozzle coating method in an amount of 20 g/m² (solidcontent) to form a first coating layer 18.

[0148] Then, a solution of Cornpol CRP-D703 (Nihon Cornstarchcorporation) which is an ester compound of lauric acid and dextrindissolved in ethyl acetate at 30% by weight (solid content) was appliedon the first coating layer 18 using a comma coater in an amount of 20 gm² (solid content) to form a second coating layer 19. Accordingly, thepackaging material 16 of Example 3 was obtained.

Comparative Example 4

[0149] In Example 3, a packaging material prior to forming the secondcoating layer 19, i.e., a packaging material having a two layeredstructure of: paper layer/first coating layer was produced to obtain thepackaging material of Comparative Example 4.

Comparative Example 5

[0150] On the reverse face of the cup body paper having the weighingcapacity of 250 g/m² used in Example 3 was formed a second coating layersimilarly to Example 3. Specifically, a composite material having a twolayered structure of: paper layer/second coating layer was produced toobtain the packaging material according to Comparative Example 5.

[0151] Experiment 8

[0152] Any one of the 3 types of packaging materials according to theaforementioned Example 1, and Comparative Examples 4 and 5 wasappropriately processed to yield a side body member and a bottom partmember. Using a generally known forming machine of paper cups, a papercup was produced having the height of 107 mm, bore diameter of 95 mm,bottom diameter of 64 mm and taper angle of 6.5° so that the paper layeris circumferentially positioned.

[0153] The moisture barrier property, oil resistance, biodegradability,and sealing property and formability upon previous formation of these 3types of the paper cup were measured and evaluated according to thefollowing process. The results are shown in Table 8.

[0154] The moisture barrier property was evaluated by charging 50 g ofcalcium chloride into a sample cup, tight sealing the cup with anappropriate lid member followed by leaving to stand in an atmosphere atthe temperature of 40° C. and humidity of 90%. Changes in weight due tothe transmitted moisture were measured, and the change in weight of lessthan 80 g/m²·day was evaluated as ◯; and the change in weight of 80g/m²·day or greater was evaluated as X.

[0155] In regard to the oil resistance, curry powder was applied oninside face of a sample paper cup, and left to stand in an atmosphere atthe temperature of 40° C. and humidity of 90% for three days. Thus, thepresence of permeation into the packaging material was determined.Absence of the permeation was evaluated as ◯; and presence of thepermeation was evaluated as X.

[0156] Biodegradability was evaluated according to JIS K6950“Plastic—Method of Testing Degree of Aerobic Biodegradation by ActivatedSludge”. Presence of degradation was evaluated as ◯; and incompletedegradation was evaluated as X.

[0157] In connection with the sealing property, the formed sample papercup was destroyed, and adhesiveness of the side body joint part and thebottom joint part was visually observed. Presence of peeling with paperscaling at the adhered part was evaluated as ◯; and absence of paperscaling leading to judgment as insufficient adhesion was evaluated as X.

[0158] In respect of the formability, machine aptitude upon forming intoa paper cup using the forming machine of paper cups was visuallyobserved. Judgment as formable without problem was evaluated as ◯; andpresence of a problem such as dissolution of the second coating layer inliquid paraffin leading to stickiness of the side body member wasevaluated as X. TABLE 8 Moisture Oil Machine Aptitude Barrier Resis-Biodegrad- Sealing Formabil- Property tance ability Property ity Example3 ◯ ◯ ◯ ◯ ◯ Comparative X X ◯ ◯ X Example 4 Comparative X ◯ ◯ ◯ ◯Example 5

[0159] Accordingly, a paper cup produced using the packaging material ofExample 3 in which the first coating layer and the second coating layerare laminated on the paper layer is a biodegradable paper cup that isexcellent in moisture barrier property and oil resistance, and hasformability. In addition, by using the ester compound of lauric acid anddextrin as a second coating layer as in Example 3, biodegradable cupshaving more excellent biodegradability and also are excellent in hotwater resistance can be obtained than those in which polylactic acid isused.

[0160] (11) Eleventh Embodiment

[0161]FIG. 12 is a cross sectional view illustrating a paper cup 23which is a container made from paper according to the eleventhembodiment. The paper cup 23 comprises an outer container 26, whichincludes a side body 24 and a bottom part 25, made from cup body paperas a principal material having an opening in an upper area, and an innercontainer 27 made from a pulp mold fit to the inside of the outercontainer 26 so that it closely contacts with the aforementioned bottompart 25. The upper marginal parts of the aforementioned outer container26 and inner container 27 are thermally fusion bound to overlay witheach other, with each upper marginal part is curled outward to form asingle portal marginal part 28.

[0162] Further, a first coating layer 29 is formed inside of the outercontainer 26, whilst the inside face of the inner container 27 is formedwith a second coating layer 30 having oil resistance and waterresistance. In addition, a heat insulation spaced layer 31 is formedbetween the bottom part of side body of the fitted inner container 27and the bottom part of side body of the outer container 26.

[0163] The first coating layer 29, which is formed inside of the outercontainer 26, having a moisture barrier property is formed on the cupbody paper 32, and is preferably a layer including a natural rubber or aderivative thereof, and a material selected from synthetic resins, waxesand derivatives thereof having permeability into paper.

[0164] The cup body paper 32 which is preferably used may be thosehaving the weighing capacity of 160 to 280 g/m² although it depends onthe finished size of the container.

[0165] The first coating layer 29 is formed on the cup body paper 32 bya comma coating method or a nozzle coating method. The thickness of thefirst coating layer 29 is preferably about 10 to 40 μm. Formation of thefirst coating layer 29 on the cup body paper 32 is preferably carriedout prior to the formation of the outer container 26.

[0166] For the second coating layer 30, which is formed inside of theinner container 27, having oil resistance and water resistance, abiodegradable resin having such properties may be used. Specificexamples thereof which can be used include natural materials such asshellac and the like, as well as ester based biodegradable reins,including for example, polylactic acid, poly 3-hydroxybutyric acid(PHB), polybutylene succinate (PBS) and modified polymerized resinsderived from starch (e.g., modified starch, having 80% or more hydroxylgroups of starch inverted with a straight chain fatty acid such aslauric acid; trade name: CPR-D703, Nihon Cornstarch corporation).

[0167] In particular, shellac is preferred on behalf of its excellentsafety because it is a natural material, and in addition, is alsoexcellent in both oil resistance and water resistance. Preferred processof applying shellac may include forming a shellac resin layer by makinga film from an aqueous solution or an alcoholic solution of shellac onthe inside face of the inner container with a spray coating method. Inthis instance, thickness of shellac is preferably about 10 to 50 μm.

[0168] Further, in regard to the outer container 26, a side body memberwhich constitutes the side body 24, and a bottom part member whichconstitutes the bottom part 25 are prepared beforehand, and formation isexecuted up to a previous step before curling the upper margin of theside body outward using a generally known forming machine of paper cups.A circular leg part 34 formed by joining the side body 24 and the bottompart 25 at the lower part of the outer container 26 may have a flatstate depending on use of the container.

[0169] As the inner container 27, a container made from a pulp mold canbe preferably used which is obtained by dissolving used paper into asolution followed by forming with a mold. For formation of the containermade from a pulp mold, a wire mesh is set on the reverse face of themold, and vacuuming is carried out from the reverse side of the mold.Then formation is completed after subjecting to a press step and adrying step.

[0170] Size of the inner container 27 is determined so that the bottomdiameter is rather smaller than the bottom diameter of the outercontainer 26, and the length of the side body is determined to besubstantially identical to the length from the joining part of the sidebody member and the bottom part member up to the upper marginal part ofthe side body member of the outer container 26. Both upper marginalparts of the middle bodies of the outer container 26 and inner container27 are thereby overlaid in a single plane when the inner container 27 isfit to the inside of the outer container 26, and the bottom part of theinner container 27 and the bottom part of the outer container 26 arebrought into close contact.

[0171] A general process for forming the paper cup 23 is explained belowwith reference to FIG. 13. First, a side body member and a bottom partmember having desired size are produced from cup body paper having afirst coating layer 29 formed on its one face. Using a generally knownforming machine of paper cups, a paper cup as the outer container 26 isproduced up to a previous step before curling the upper margin of theside body outward with the first coating layer 29 positioned to be aninner face (see, FIG. 13(a)). A container made from a desired pulp moldis separately prepared as the inner container 27 (see, FIG. 13(b)).

[0172] The inner container 27 is then fit to the inside of the outercontainer 26 followed by thermal fusion binding of the bottom parts andupper marginal circumferences of the middle bodies which shall becomecontact sites of the outer container 26 and inner container 27 (see,FIG. 13(c)).

[0173] On the inner face of the inner container 27 of thus produceddouble container applied an aqueous solution or an alcoholic solution ofa shellac resin with a spray coating method followed by heating to formthe second coating layer 30. It should be noted, however, that thesecond coating layer 30 may be formed before the previous step to givethe double container, for example, may be formed concurrently with theproduction of the inner container 27.

[0174] Finally, the upper marginal part of the side body of this doublecontainer is curled outward to form a portal marginal part 28 to obtainthe paper cup 23 having a heat insulation spaced layer 31 between thelower outside part of side body of the inner container 27 and the lowerinside part of side body of the outer container 26 (see, FIG. 13(d)).

[0175] Upon formation of the portal marginal part 28 of this doublecontainer, it is preferred that formation is executed as described abovethrough overlaying both upper marginal parts of the middle bodies of theouter container 26 and inner container 27 in a single plane, however forexample, the following process shall be also possible. Specifically,according to the process, the side body of the inner container 27 isformed such that the upper marginal part of the side body thereof israther higher than that of the outer container 26, and the uppermarginal part of the outer container 26 is thermally fusion bound at aslightly lower site (peripheral part) of the upper marginal part of theinner container 27. Through curling the upper marginal circumference ofthe side body of the inner container 27 outward, formation is executedinto such a shape that has the upper marginal part of the side body ofthe outer container 26 inserted in this curled portion.

[0176] Furthermore, in either instance described above, the thermalfusion binding step of the outer container 26 and the inner container 27is not limited to prior to curling of the portal marginal part of thedouble container, but can be also carried out as the step followingformation of the curling of the portal marginal part. Furthermore theportal marginal part may be also processed into a flat shape dependingon the intended use, through hot pressing of the curled portal marginalpart in a vertical direction (see, FIG. 13(e)).

[0177] Although a container 23 was provided herein having the innercontainer 27 made from a pulp mold and the outer container made frompaper in combination as the eleventh embodiment, to the contrary, acontainer can be also provided having a container made from a pulp moldas an outer container, and a container made from paper as an innercontainer combined therewith.

[0178] In this instance, it is preferred that the inside face of thecontainer made from paper forming the inner container shall be thesecond coating layer having oil resistance and water resistance, whilethe outside face of the inner container shall be the first coating layerhaving a moisture barrier property. More specifically, the packagingmaterial made from paper according to the present invention is obtainedby laminating: first coating layer/paper layer/second coating layer inthis order, and then this packaging material is formed into an innercontainer with the second coating layer being an inside face thereof.Accordingly, production is perfected through fitting this innercontainer to the inside of the container made from a pulp mold. By usinga pulp mold for the outside of the container, the container becomes morerigid than the container with its outside made from paper.

[0179] Moreover, similarly to the eleventh embodiment shown in FIG. 12,the thermal insulation property of the container can be improved byforming a space between the outer container and the inner containerthrough making the container into a cupped shape and making the sidebody of the outer cup made from a pulp mold into the tapered shape withmore enlarged lower part than the side body of the inner paper cup.

[0180] The structure of the inner container made from paper which is fitinto the outer container made from a pulp mold is not necessarily alamination structure of: first coating layer/paper layer/second coatinglayer, but for example, those having a structure of: paper layer/firstcoating layer/paper layer/second coating layer as in Example 1, or astructure of: paper layer/first coating layer/second coating layer as inExample 3 may be allowed, either of which is formed such that the secondcoating layer becomes an inside face of the container.

EXAMPLE

[0181] The eleventh embodiment is explained below in more detail by wayof Example.

Example 4

[0182] On one face of cup body paper 32 having the weighing capacity of220 g/m² was applied a butyl acetate solution of a mixture of a naturalrubber/modified rosin/carnauba wax/sorva/shellac/glycerin fatty acidester=20/64.4/7.6/4/3.2/0.8 (solid content: 40%) by a comma coatingmethod in an amount of 25 g/m² to form the first coating layer 29.

[0183] A side body member and a bottom part member having desired sizewere produced from this cup body paper 32 having the first coating layer29 formed on its one face. Then, using a generally known forming machineof paper cups, a paper cup as the outer container 26 was produced up toa previous step before curling the upper marginal part of the side bodyoutward with the first coating layer 29 positioned to be an inner face.

[0184] A container made from a pulp mold having desired size wasseparately prepared as the inner container 27. On the inner face of thispulp mold container was applied an ethanol solution of shellac (solidcontent: 25%) by a spray coating method followed by drying to form afilm. Accordingly, the second coating layer 30 having the thickness of30 μm, and having oil resistance and water resistance was formed.

[0185] The inner container 27 was then fit to the inside of the outercontainer 26 to give a double container, followed by thermal fusionbinding of the bottom parts and upper marginal circumferences of themiddle bodies which shall become contact sites of the outer container 26and inner container 27. Thereafter, the upper marginal part of the sidebody of this double container was curled to form a portal marginal part28 to obtain the paper cup 23 of Example 4, which was produced using abiodegradable packaging material, having a heat insulation spaced layer31 between the lower outside part of side body of the inner container 27and the lower inside part of side body of the outer container 26 (see,FIG. 12).

Comparative Example 6

[0186] To the outer face of the inner container 27 made from a pulp moldhaving the second coating layer formed on its inner face used in Example6 was adhered cup body paper having the weighing capacity of 220 g/m²for both the side body and the bottom part with a hot melt adhesive.Thereafter, the upper marginal part of the side body was curled outwardto form a portal marginal part to obtain the paper cup of ComparativeExample 6.

[0187] Experiment 9

[0188] The moisture barrier property, oil resistance, biodegradability,and thermal insulation property of the two types of the paper cup ofExample 4. and Comparative Example 6 described above were measured andevaluated according to the following process. The results are shown inTable 9.

[0189] The moisture barrier property was evaluated by charging 50 g ofcalcium chloride into a sample cup, tight sealing the cup with anappropriate lid member followed by leaving to stand in an atmosphere atthe temperature of 40° C. and humidity of 90%. Changes in weight due tothe transmitted moisture were measured, and the change in weight of lessthan 80 g/m²·day was evaluated as ◯; and the change in weight of 80g/m²·day or greater was evaluated as X.

[0190] In regard to the oil resistance, curry powder was applied on thesecond coating layer side of the inner container of a sample paper cup,and left to stand in an atmosphere at the temperature of 40° C. andhumidity of 90% for three days, and the presence of permeation into thesecond coating layer was determined. Absence of the permeation wasevaluated as ◯; and presence of change in color due to the curry powder,i.e., presence of the permeation was evaluated as X.

[0191] Biodegradability was evaluated according to JIS K6950“Plastic—Method of Testing Degree of Aerobic Biodegradation by ActivatedSludge”. Presence of degradation was evaluated as ◯; and residual hotmelt adhesive, i.e., incomplete degradation was evaluated as X.

[0192] In connection with the thermal insulation property, hot water waspoured into a sample paper cup followed by leaving to stand for 5minutes. Thereafter, side body of the paper cup was held with a hand,and thermal insulation effects and permeation into the container weredetermined. Capability of easy holding with a hand, accompanied byabsence of permeation or leakage in the container was evaluated as ◯;and incapability of holding with a hand owing to hot was evaluated as X.TABLE 9 Moisture barrier Thermal property Oil insulation (g/m² · day)resistance Biodegradability property Example 4 20 or less ◯ ◯ ◯ (◯)Comparative 80 or greater ◯ X ◯ Example 6 (x)

[0193] Accordingly, the paper cup according to Example 4 comprising aninner container made from a pulp mold having a second coating layerapplied on its inner face, which is fit into an outer container madefrom cup body paper having a first coating layer applied on its innerface which layer consists of a layer including a natural rubber,modified rosin, carnauba wax, sorva and shellac is revealed to be apaper container which is excellent in moisture barrier property, oilresistance, biodegradability and thermal insulation property.

[0194] (12) Twelfth Embodiment

[0195]FIG. 14 is a cross sectional view illustrating a layered structureof a packaging material 36 according to the twelfth embodiment. In FIG.14, 37 denotes a paper layer, 38 denotes a first coating layer having amoisture barrier property, and 39 denotes a second coating layer.

[0196] One face 37 a of the paper layer 37 is subjected to clay coating.The first coating layer 38 is thereby formed on the paper layer 37 viathe clay coating. Therefore, unnecessary permeation into the paper layer37 of a solvent in a solution of a natural rubber which constitutes thefirst coating layer 38 can be prevented. Hence, excess amount of thefirst coating layer is not necessarily applied, which enables thereduction of residual odor. It is preferred that the clay coating isformed in an amount of approximately 2 to 15 g/m².

[0197] The first coating layer 38 is a layer which is responsible forthe moisture barrier property, and includes a natural rubber or aderivative, and a material selected from synthetic resins, waxes andderivatives thereof having permeability into paper.

[0198] Through application of the first coating layer 38 in an amount of10 to 70 g/m², preferably 20 to 50 g/m², the moisture barrier propertyalmost equivalent to polyethylene can be accomplished.

[0199] The aforementioned natural rubber or a derivative thereof, and amaterial selected from synthetic resins, waxes and derivatives thereofhaving permeability into paper are dissolved in an organic solvent suchas toluene, ethyl acetate or the like, preferably ethyl acetate. Thissolution is applied on a face 37 a of the paper layer 37 which wassubjected to clay coating, in an amount of approximately 20 to 50 g/m²converted as a solid content with a known application method such asroll coating method, and dried.

[0200] The second coating layer 39 is a layer having oil resistance anda sealant property, of which base material may be polylactic acid (PLA),poly 3-hydroxybutyric acid (PHB), polybutylene succinate (PBS), amodified polymerized resin derived from starch or a mixture thereof, ashellac resin or the like.

[0201] (13) Thirteenth Embodiment

[0202]FIG. 15 is a cross sectional view illustrating a layered structureof a packaging material 40 according to the thirteenth embodiment.Difference of the layered structure of the packaging material 40 fromthat of the packaging material 36 of the twelfth embodiment is limitedonly to the presence of the second paper layer 41 between the firstcoating layer 38 and the second coating layer 39. Such a constitutionenables lamination of these layers even if adhesion involves difficultybetween the first coating layer 38 and the second coating layer 39.

[0203] When the paper layer 37 has the weighing capacity of 50 to 140g/m² and the density of 0.88 to 1.0 g/cm³, the second paper layer 41which may be used preferably has the weighing capacity of 100 to 300g/m² and the density of 0.85 to 1.0 g/cm³.

[0204] Although not shown in the figure, the face 41 a, which is to bebrought into contact with the first coating layer 38, of the secondpaper layer 41 can be also subjected to clay coating, and in thisinstance, unnecessary permeation into the second paper layer 41 of asolvent in a solution of a natural rubber which constitutes the firstcoating layer 38 can be prevented. Further, a clay layer can be alsoformed to the face 41 b, which is to be brought into contact with thesecond coating layer 39, of the second paper layer 41. In this instance,permeation into the paper layer 41 of the components that constitute thesecond coating layer 39 can be suppressed, leading to advantages ofpossible reduction of the application amount of the second coating layer39.

[0205] In the process for producing the packaging material 40, hotpressing lamination of the paper layer 37 having the applied firstcoating layer 38 and the paper layer 41 is conducted so that the firstcoating layer 38 is sandwiched therebetween. Finally, the second coatinglayer 39 is applied on the face, which is not contacted with firstcoating layer 38, of the paper layer 41 to give the packaging material40.

[0206] Alternatively, the packaging material 40 may be obtained throughhot pressing lamination of the paper face of the paper layer 41 havingthe laminated second coating layer 39, allowed to be opposed to thepaper layer 37 having the applied first coating layer 38.

[0207] Examples of the applicable method for lamination of the secondcoating layer 39 onto the paper layer 41 include lamination methods suchas an extrusion lamination method, a hot pressing lamination method

[0208] (14) Fourteenth Embodiment

[0209]FIG. 16 is a perspective view illustrating a paper cup 42 which isa container made from paper according to the fourteenth embodiment. Thepaper cup 42 may be produced by appropriate processing of the packagingmaterial 36 or 40 according to the twelfth or thirteenth embodiment togive the side body member and the bottom part member, and then anygenerally known forming machine of paper cups is used.

EXAMPLE

[0210] The twelfth to fourteenth embodiments are explained below in moredetail by way of Example.

Example 5

[0211] As a paper layer 37, single face coated cup body paper having theweighing capacity of 70 g/m² and the density of 0.9 g/cm³ with one face37 a which had been subjected to clay coating in an application amountof 10 g/m² was prepared, whilst as a paper layer 41, no coated cup bodypaper having the weighing capacity of 220 g/m² and the density of 0.9g/cm³ was prepared.

[0212] Separately, a solution of the natural rubber material (solidcontent: 50%, solvent: ethyl acetate) blended in a mixing ratio of:natural rubber/modified rosin/carnauba wax/ester gum/guttapercha=20/57/7/8/2 was applied on the clay coated face 37 a of the paperlayer 37 by a gravure coating method, and dried (application amount: 30g/m² (solid content)) to form the first coating layer 38.

[0213] Additionally, to the no coated cup body paper 14 which had beenpreviously prepared was laminated polylactic acid (PLA), which shall bethe second coating layer 39, prepared so that the application amountbecomes 20 g/m² by a melt extrusion lamination method.

[0214] Finally, the packaging material 40 of Example 5 was producedhaving a layered structure of: paper layer 37/first coating layer38/second paper layer 41/second coating layer 39 through hot pressinglamination of the paper layer 37 having the applied first coating layer38 and the paper layer 41 having the laminated first coating layer 39 byallowing the first coating layer 38 to be opposed to the paper layer 41under a condition at the temperature of 140° C. and the pressure of 0.31MPa (lamination velocity: 50 m/min).

Comparative Example 7

[0215] A packaging material of Comparative Example 7 having the layeredstructure of: paper layer/first coating layer/second paper layer/secondcoating layer was produced with the same materials and same condition asin Example 5 except that no coated cup body paper was used having theweighing capacity of 70 g/m² and the density of 0.9 g/cm³ with no claycoated on the paper layer.

[0216] Experiment 10

[0217] Thickness of the first coating layer, moisture barrier property,residual odor, cup formability of the two types of the packagingmaterial of Example 5 and Comparative Example 7 described above weremeasured and evaluated according to the following process. In connectionwith the moisture barrier property, residual odor, cup formability, thepaper cup 42 as shown in FIG. 16 was produced with the aforementionedtwo types of packaging material, and was subjected to the measurementand evaluation. The results are shown in Table 10.

[0218] Thickness of the first coating layer was measured with athickness indicator.

[0219] The moisture barrier property was measured according to JISZ0208.

[0220] The residual odor was measured by gas chromatography(manufactured by Hewlett-Packard Co.). Upon the measurement, temperedglass which had been subjected to silane finishing was used as a column.

[0221] Evaluation of cup formability was carried out through forming acup using a general forming machine of paper cups, and observation ofthe formability (formation velocity: 120 cups/min.). Absence of theproblem was evaluated as ◯; and

[0222] presence of incomplete side sealing was evaluated as X. TABLE 10Thickness of Moisture vapor Residual first coating transmission odor Cuplayer (μm) rate (g/m²) (ppm) formability Example 5 30 20 500

◯ Comparative 20 40 2000 ◯ Example 7

[0223] Accordingly, the paper cup obtained using the packaging materialof Example 5 with the paper layer 37 which had been subjected to claycoating was revealed to be a biodegradable container made from paperexhibiting less unevenness in thickness of the first coating layer 38,and was excellent in moisture barrier property with less residual odor.

[0224] (15) Fifteenth Embodiment

[0225]FIG. 17 is a cross sectional view illustrating a layered structureof a packaging material 110 according to the fifteenth embodiment. InFIG. 17, 115 denotes an oil resistant layer, 113 denotes a first coatinglayer containing a natural rubber, 111 denotes a first paper layer, 114denotes a second coating layer containing a natural rubber, 112 denotesa second paper layer, and 116 denotes a sealant layer. The packagingmaterial 110 has a construction including each layer laminated in theorder described above.

[0226] The oil resistant layer 115 is provided for the purpose of:preventing the coating layer containing a natural rubber from adsorptionand permeation of machine oil or lubricating oil for formation which ispresent during the formation of the container, on behalf of thepositioning of the coating layer containing a natural rubber 113 on theoutermost face of the container; and of preventing adhesiveness andstickiness of the coating layer containing a natural rubber depending onthe mixing ratio of the components. Therefore, when such events can beprevented by other means, there exits no need to provide the oilresistant layer.

[0227] The oil resistant layer 115 is preferably formed by applying asolution of a material, which is a modified polymerized resin derivedfrom starch whose hydroxyl groups were inverted by 80% or greater with astraight chain fatty acid such as lauric acid, in an organic solvent tothe paper layer 113. However, in addition thereto, a biodegradable resinor a synthetic resin is applicable as long as it has oil resistance.Moreover, the application amount of the oil resistant layer 115 may beapproximately 5 to 20 g/m² (solid content).

[0228] The first coating layer containing a natural rubber 113 and thesecond coating layer containing a natural rubber 114 comprise a naturalrubber or a derivative thereof, and a material selected from naturalresins, waxes and derivatives thereof having permeability into paper,with the application amount being approximately 10 to 30 g/m² (solidcontent).

[0229] The coating layers containing a natural rubber 113 and 114 can beformed using an application liquid which includes similar materials tothose for the first coating layers according to other embodiments.

[0230] Thus, more sufficient moisture barrier property can be impartedto matters to be packed according to this embodiment through providingtwo coating layers containing a natural rubber, in comparison with theinstance to provide the coating layer containing a natural rubber as asingle layer.

[0231] The first paper layer 111 preferably used herein may be cup bodypaper having the weighing capacity of 50 to 140 g/m² and the density of0.88 to 1.0 g/cm³ with clay coated on both faces 111 a. Such a claycoated structure is provided for the purpose of: preventing reduction ofthe moisture barrier property on behalf of permeation into the paperlayer 111 of the material in the coating layer containing a naturalrubber, leading to failure of securement of the thickness of the coatinglayers containing a natural rubber 113 and 114; and of preventinggeneration of odor due to permeation of the natural rubber or thesolvent into the paper layer 111.

[0232] The second paper layer 112 preferably used may be no coated cupbody paper having the weighing capacity of 100 to 300 g/m² and thedensity of 0.85 to 1.0 g/cm³ without being subjected to clay coating.Through the use of such a no coated cup without being subjected to claycoating, adhesiveness between the paper layer 112 and the coating layer114 containing a natural rubber is improved. However, cup body papersubjected to clay coating may be also used for the purpose of preventingreduction of the moisture barrier property and generation of odorresulting from permeation of the natural rubber or the solvent into thepaper layer 112.

[0233] Furthermore, when a material having high permeability into papersuch as a shellac resin or the like is used as the material of thesealant layer 116, the face on the sealant layer 116 side of the secondpaper layer 112 may be also subjected to clay coating in order toprevent permeation thereof into the paper layer 112.

[0234] The sealant layer 116 is provided by applying a biodegradableresin into a film, and examples of the biodegradable resin which can beused include materials used in the second coating layer according toother embodiments, i.e., polylactic acid, poly 3-hydroxy butyric acid(PHB), polybutylene succinate (PBS), a modified polymerized resinderived from starch (Cornpol), shellac and the like. Hence, the sealantlayer 116 is a layer provided by applying a biodegradable resin having asealant property into a film, favorable sealing property can be achievedin use for forming a container. In addition, through using thebiodegradable resin as described above, oil resistance is imparted, andalso water resistance is improved.

[0235] (16) Sixteenth Embodiment

[0236]FIG. 18 is a cross sectional view illustrating a paper cup 120which is a container made from paper according to the sixteenthembodiment. The paper cup 120 is produced by appropriate processing ofthe packaging material 110 according to the fifteenth embodiment to givethe side body member and the bottom part member, and then any generallyknown forming machine of paper cups is used. For the bottom part member,a packaging material with no oil resistant layer 115 formed may be used.Further, the paper layer 111 may not be subjected to clay coating.

[0237] The paper cup 120 is a paper cup formed by a thermal adhesionmethod which includes a side body 43 and a bottom part 44, and has aportal marginal part 45 with the marginal circumference of the openingcurled outward. The longitudinal end face 46 of the inner face side ofthe side body 43 is subjected to skived hemming processing. The papercup 120 is formed so that the sealant layer 116 of the packagingmaterial 110 is brought to be the inner face side of the container forboth of the side body 43 and the bottom part 44.

[0238] Skived hemming processing is explained below with reference tothe cross sectional view shown in FIG. 19. The cross sectional viewshown in FIG. 19 presents a cross section cut with the Y-Y line depictedin FIG. 18. The skived hemming processing according to this embodimentis accomplished by deleting one longitudinal end face 121 of the sidebody member by substantially half thickness 122 of the side body memberin a predetermined length from the top (skive) (see, FIG. 19(a)), andthe remaining part 123 after deletion is turned such that the deletedface becomes inner side (hemming) (see, FIG. 19(b)), to protect the endface of the side body member. Thus turned surfaces which had beendeleted are allowed to adhere with each other using the starch glue.

[0239] When the paper end face is exposed to the inner face of the papercup, the ingredient is permeated therefrom into the packaging materialleading to deterioration of the container strength of the paper cup.However, according to this embodiment, skived hemming processing isexecuted thereby preventing such an event.

[0240] In addition, because the skived hemming processing results inlamination of the same sealant layers 116 with each other upon formationof the paper cup 120 (see, FIG. 19(c)), formability of the container isimproved.

EXAMPLE

[0241] The fifteenth to sixteenth embodiments are explained below inmore detail by way of Example.

Example 6

[0242] Cup body paper having the weighing capacity of 70 g/m² with claycoated on both faces 111 a in an amount of 8 g/m² was prepared as afirst paper layer 111, and no coated cup body paper having the weighingcapacity of 220 g/m² was prepared as a first paper layer 112.

[0243] Separately, a solution of the natural rubber material (solidcontent: 50%, solvent: butyl acetate) blended in a mixing ratio of:natural rubber/modified rosin/carnauba wax/ester gum/guttapercha=20/57/7/8/2 was applied on both faces of the first paper layer111 by a roll coating method, and dried (application amount: each 15g/m² (solid content)) to form the first coating layer containing anatural rubber 113 and the second coating layer containing a naturalrubber 114.

[0244] Additionally, on the first coating layer containing a naturalrubber 113 was applied a solution of a modified polymerized resinderived from starch comprising CPR-D703 (Nihon Cornstarch corporation)(solid content: 35%, solvent: ethyl acetate) by a roll coating methodfollowed by drying (application amount: 20 g/m² (solid content)) to forman oil resistant layer 115.

[0245] Separately, polylactic acid (PLA) which shall be the sealantlayer 116 was prepared, and laminated by a melt extrusion laminationmethod so that the application amount becomes 20 g/m² to the no coatedcup body paper which is the second cup body paper 112 that had beenpreviously prepared.

[0246] Then, the packaging material 110 was produced having a layeredstructure of: oil resistant layer 115/first coating layer containing anatural rubber 113/first paper layer 111/second coating layer containinga natural rubber 114/second paper layer 112/sealant layer 116 by hotpressing lamination of the first cup body paper 111 having the firstcoating layer containing a natural rubber 113, the second coating layercontaining a natural rubber 114 and the oil resistant layer 115 applied,and the second cup body paper 112 having the sealant layer 116laminated, through allowing the second coating layer containing anatural rubber 114 face to be opposed to the second cup body paper 112face under a condition at the temperature of 140° C. and the pressure of0.31 MPa (lamination velocity: 50 m/min).

[0247] Such a packaging material 110 was punched out to give apredetermined sized substantially sectorial shape, and one longitudinalend face was subjected to skived hemming processing to provide the sidebody member.

[0248] Next, the bottom part member was produced. Cup body paper havingthe weighing capacity of 70 g/m² was prepared as the first cup bodypaper 111, and on one face of this cup body paper was applied a coatinglayer containing a natural rubber having the identical formulation tothat used upon producing the side body member so that the applicationamount became 30 g/m² (solid content) by the identical method to thatadopted upon producing the side body. Additionally, also as the secondpaper layer 112, similar no coated cup body paper having the weighingcapacity of 220 g/m² to one used upon producing the side body wasprepared. Thus, polylactic acid (PLA) which shall be the sealant layerwas prepared, and laminated to one face by a melt extrusion laminationmethod so that the application amount becomes 200 g/m².

[0249] Then, the bottom part member having the layered structure of:first paper layer/coating layer containing a natural rubber/second paperlayer/sealant layer was produced by hot pressing lamination of the firstcup body paper having the coating layer containing a natural rubberapplied, and the second cup body paper having the sealant layerlaminated, through allowing the coating layer containing a naturalrubber to be opposed to the second cup body paper under a condition atthe temperature of 140° C. and the pressure of 0.31 MPa (laminationvelocity: 50 m/min).

[0250] Using the side body member and the bottom part member produced insuch a manner, a paper cup, which includes the second coating layerhaving the sealant property provided inside and has a portal marginalpart, was formed with a generally known forming machine of paper cupshaving the height of 90 mm, bore diameter of 88 mm, and taper angle of6.50 to give the paper cup of Example 6.

Comparative Example 8

[0251] Using the packaging material having the layered structure of:first paper layer/coating layer containing a natural rubber/second paperlayer/sealant layer, which was used as the bottom part member in Example6 for both of the side body member and the bottom part member, a papercup was formed in a similar manner to Example 6 to obtain the paper cupof Comparative Example 8. However, the side body member was notsubjected to the skived hemming processing.

[0252] Experiment 11

[0253] Cup formability and moisture barrier property of the two types ofthe paper cup of Example 6 and Comparative Example 8 described abovewere observed and evaluated according to the following process. Theresults are shown in Table 11.

[0254] Evaluation of cup formability was carried out by visuallyobserving the formability. Absence of the problem was evaluated as ◯;and presence of incomplete side sealing was evaluated as X.

[0255] The moisture barrier property was evaluated by charging 50 g ofcalcium chloride into a sample paper cup, tight sealing, followed byleaving to stand in an atmosphere at the temperature of 40° C. andhumidity of 90%. An amount of transmitted moisture per one day wasmeasured on the basis of changes in weight after leaving, and thedetermination as sufficient moisture barrier property was evaluated as◯; and determination as not sufficient moisture barrier property wasevaluated as Δ. In instances of the measurement was not performed,evaluation was represented as -. TABLE 11 Cup Moisture barrierformability property Example 6 ◯ ◯ (1.0 g/cup) Comparative Example 8 ◯ Δ(2.5 g/cup)

[0256] Accordingly, the paper cup which includes double coating layerscontaining a natural rubber and is subjected to skived hemmingprocessing of the end face of the side body member is revealed to havefurther improved moisture barrier property.

What is clamed is:
 1. A packaging material having a paper layer and afirst coating layer laminated thereon, said first coating layercomprises a first material and a second material, wherein the firstmaterial is a natural rubber or a derivative thereof, and the secondmaterial is a material selected from natural resins, waxes andderivatives thereof having permeability into paper.
 2. A packagingmaterial having a paper layer, a first coating layer and a secondcoating layer laminated in this order, said first coating layercomprises a first material and a second material, wherein the firstmaterial is a natural rubber or a derivative thereof, and the secondmaterial is a material selected from natural resins, waxes andderivatives thereof having permeability into paper, and said secondcoating layer has oil resistance and consists of a biodegradablematerial.
 3. A packaging material having a first coating layer, a paperlayer and a second coating layer laminated in this order, said firstcoating layer comprises a first material and a second material, whereinthe first material is a natural rubber or a derivative thereof, and thesecond material is a material selected from natural resins, waxes andderivatives thereof having permeability into paper, and said secondcoating layer has oil resistance and consists of a biodegradablematerial.
 4. A packaging material having a paper layer, a first coatinglayer, a paper layer and a second coating layer laminated in this order,said first coating layer comprises a first material and a secondmaterial, wherein the first material is a natural rubber or a derivativethereof, and the second material is a material selected from naturalresins, waxes and derivatives thereof having permeability into paper,and said second coating layer has oil resistance and consists of abiodegradable material.
 5. A packaging material having an oil resistantlayer, a first coating layer, a paper layer, a first coating layer, apaper layer and a second coating layer laminated in this order, saidfirst coating layer comprises a first material and a second material,wherein the first material is a natural rubber or a derivative thereof,and the second material is a material selected from natural resins,waxes and derivatives thereof having permeability into paper, said oilresistant layer consists of a biodegradable material, and said secondcoating layer has oil resistance and a sealant property, and consists ofa biodegradable material.
 6. The packaging material according to any oneof claims 1 to 5 wherein said second material is at least one selectedfrom the group consisting of ester gum, dammar, copal, copaiba balsam,benzoin gum, gum olibanum, opopanax, sandarac, Guaiac, mastic, myrrha,Leche de vaca, kauri gum, rosin, fir balsam, elemi, chicle, jelutong,sorva, Venezuela chicle, niger gutta, Chilte, gutta katiau, Tunu,sorbinba, Massaranduba chocolate, Massaranduba balata, balata,Rosidinha, guayule, gutta percha, gutta percha, shellac, urucury wax,carnauba wax, candelilla wax, whale wax, rice bran wax, sugarcane wax,bees wax, wood wax, montan wax, oil stuff seed wax and lanolin.
 7. Thepackaging material according to claim 6 wherein said second materialcomprises ester gum.
 8. The packaging material according to any one ofclaims 1 to 5 wherein the ratio of said first material in said firstcoating layer is 70% by weight or less.
 9. The packaging materialaccording to claim 8 wherein the ratio of said first material in saidfirst coating layer is in the range of from 20 to 50% by weight.
 10. Thepackaging material according to any one of claims 2 to 5 wherein thebiodegradable material of said second coating layer is at least oneselected from the group consisting of poly 3-hydroxybutyric acid,polylactic acid, polylactic acid derivatives, polybutylene succinate,modified polymerized resins derived from starch, and a shellac resin.11. The packaging material according to claim 10 wherein thebiodegradable material of said second coating layer is a modifiedpolymerized resin derived from starch, and said modified polymerizedresin is an ester compound having the blocking ratio of hydroxyl groupswith lauric acid and dextrin of 80% or greater.
 12. The packagingmaterial according to any one of claims 1 to 5 wherein at least one faceof said paper layer is clay coated.
 13. The packaging material accordingto claim 12 wherein the face of said paper layer to be laminated withsaid first coating layer is clay coated.
 14. A container which isproduced using the packaging material according to any one of claims 1to
 13. 15. A container which is produced using the packaging materialaccording to any one of claims 2 to 5, and is produced so that saidsecond coating layer becomes an inside face of the container.
 16. Acontainer which comprises paper having at least a first coating layerlaminated thereon, and a biodegradable material, said first coatinglayer comprises a first material and a second material, wherein thefirst material is a natural rubber or a derivative thereof, and thesecond material is a material selected from natural resins, waxes andderivatives thereof having permeability into paper.
 17. The containeraccording to any one of claims 14 to 16 which comprises a cylindricalside body.
 18. A container which comprises an outer container of whichbase material is paper, and an inner container made from a pulp moldwhich is fit to inside of said outer container, wherein the inside faceof said outer container has a first coating layer formed, and the insideface of said inner container has a second coating layer formed, saidfirst coating layer comprises a first material and a second material,wherein the first material is a natural rubber or a derivative thereof,and the second material is a material selected from natural resins,waxes and derivatives thereof having permeability into paper, and saidsecond coating layer has oil resistance, and consists of a biodegradablematerial.
 19. The container according to claim 18 wherein thebiodegradable material of said second coating layer is a shellac resin.20. A container which comprises an outer container made from a pulpmold, and an inner container which is fit to inside of said outercontainer, of which base material is paper, wherein the outside face ofsaid inner container has a first coating layer formed, the inside faceof said inner container has a second coating layer formed, said firstcoating layer comprises a first material and a second material, whereinthe first material is a natural rubber or a derivative thereof, and thesecond material is a material selected from natural resins, waxes andderivatives thereof having permeability into paper, and said secondcoating layer has oil resistance, and consists of a biodegradablematerial.
 21. The container according to any one of claims 18 to 20wherein a spaced layer is formed to a part of the facing zone betweensaid inner container and said outer container.
 22. A process forproducing a container using a packaging material having at least a paperlayer and a first coating layer laminated, and a biodegradable sealantlayer laminated to the outermost face, in such a manner to allow a partof said packaging material is overlaid, said first coating layercomprises a first material and a second material, wherein the firstmaterial is a natural rubber or a derivative thereof, and the secondmaterial is a material selected from natural resins, waxes andderivatives thereof having permeability into paper, and said processcomprises a skived hemming processing performed such that the outermostface of the end face of the overlaid part where said packaging materialis overlaid becomes said sealant layer.
 23. A container produced using apackaging material having at least a paper layer and a first coatinglayer laminated, and a biodegradable sealant layer is laminated to theoutermost face, wherein a side body is formed by overlaying the end toan end of said packaging material such that said sealant layer ispositioned to the inside face, said first coating layer comprises afirst material and a second material, wherein the first material is anatural rubber or a derivative thereof, and the second material is amaterial selected from natural resins, waxes and derivatives thereofhaving permeability into paper, and wherein skived hemming processing iscarried out such that the outermost face of the end face of the overlaidpart where said packaging material is overlaid becomes said sealantlayer.